1. Field of the Invention
The present invention relates to an inner cutter for an electric rotary shaver and to a rotary type electric shaver.
2. Prior Art
A conventional electric rotary shaver will be described with reference to FIGS. 7 and 8.
First, to describe the overall structure, the electric shaver 10 is substantially comprised of a main body case 16 and a cutter head section 24. The main body case 16 is made of a synthetic resin and is held in hand of the user when hair, beard, mustache, etc. (called xe2x80x9chairxe2x80x9d) is shaved. The main body case 16 contains, along with other components, a motor 12, a power supply switch 14 and a power supply part (not shown) that supplies electric power to the motor 12. The cutter head section 24 is detachably mounted on the upper end of the main body case 16 and has outer cutters 18, inner cutters 20 and inner cutter bases 22 for the inner cutters 20, etc. that are built into the cutter head section 24.
FIGS. 7 and 8 show an electric shaver 10 in which three outer cutters 18 are installed in the cutter head section 24 so that the centers of three outer cutters 18 are positioned substantially at the vertices of an equilateral triangle. However, there are no restrictions on the number of outer cutters 18. The outer cutters 18 (and the corresponding inner cutters 20) can be one, two or four or more.
Inner cutter drive shafts 28 made of a synthetic resin are installed so as to protrude (in a number equal to the number of inner cutters 20) from a cutter cradle 26 that covers the opening part in the upper portion of the main body case 16. The inner cutter drive shafts 28 transmit the rotational force of the motor 12 to the inner cutters 20 installed in the cutter head section 24. When the cutter head section 24 is mounted on the main body case 16 (or more specifically attached to the cutter cradle 26 of the main body case 16), the tip ends of the inner cutter drive shafts 28 are connected by an interlocking engagement to the inner cutter bases 22 to which the inner cutters 20 are attached. Also, the inner cutters 20 receive a rotational force from the inner cutter drive shafts 28 and rotate as a unit with the inner cutter drive shafts 28.
Next, the structures of the respective components of the electric shaver will be described in detail.
First, the cutter head section 24 is comprised of a cutter frame 30 made of a synthetic resin, outer cutters 18 made of metal, an outer cutter holder 32 which is made of a synthetic resin and holds the outer cutters 18, inner cutters 20 made of metal, inner cutter bases 22 which are made of a synthetic resin and to which the inner cutters 20 are attached, and a cutter retaining plate 34 which is made of a synthetic resin and which holds the inner cutters 20 so that the inner cutters 20 are rotatable.
The metal outer cutters 18 are formed so that the overall shape of the outer cutters 18 is a shape derived by inverting a cylindrical body which has a bottom and which has a low height (i.e., an inverted dish shape or cap shape). An annular outside hair introduction region V, and an annular inside hair introduction region W positioned to the inside of the outside hair introduction region V, are formed concentrically in the upper-surface portion of each outer cutter 18 which contacts the skin.
Furthermore, a positioning engaging portion 36 (as one example in the shape of a recess) is formed in the undersurface of the region X located within the inside hair introduction region W of each outer cutter 18. The positioning engaging portion 36 prevents wobbling of the rotational axis of each inner cutter 20 with respect to the corresponding outer cutter 18 by engaging in an interlocking manner with the end portion of the corresponding inner cutter base (described later), so that each inner cutter 20 constantly rotates coaxially with the corresponding outer cutter 18
A plurality of hair introduction openings 40 are opened in the inside and outside hair introduction regions V and W. In FIG. 7, the hair introduction openings are formed as slits that extend from the outer side to the inner side of the respective hair introduction regions V and W. Scattered small holes having a round shape, oval shape or slot-form shape may be used as the hair introduction openings 40.
Furthermore, the surfaces of the respective hair introduction regions V and W are formed as flat surfaces; in the case of the outer cutter 18 shown in FIG. 8, the respective hair introduction regions V and W are formed (as one example) so that they are positioned in the same plane.
Each one of these outer cutters 18 is mounted in a corresponding outer cutter holder 32 made of a synthetic resin so that: the outer cutter 18 is not rotatable, the amount of protrusion of the outer cutter 18 form the outer cutter holder 32 can be altered, and the outer cutter 18 is tiltable in all directions within a specified angular range inside the outer cutter holder 32.
Furthermore, the outer cutters 18 are mounted together with the outer cutter holder 32 in the cutter frame 30 so that the tip ends of the outer cutters 18 protruded from outer cutter holes 42 formed in the cutter frame 30. Since the internal diameter of the outer cutter holes 42 is formed so that it is slightly larger than the external diameter of the outer cutters 18, the outer cutters 18 are mounted in the cutter frame 30 so that the amount of protrusion of the outer cutters from the cutter frame 30 can be varied by the movement of the outer cutters 18 along the axial lines of the outer cutter hole 42, and so that the outer cutters 18 can be tilted in all directions with respect to the axial lines of the outer cutter holes 42 within a specified angular range.
As shown in FIGS. 8 and 9, the metal outer cutter 20 is comprised of a cutter supporting member 21 and a plurality of inner cutter bodies 23. The cutter supporting member 21 has a ring-form body 21a, which is formed in the shape of a flat plate, and a plurality of upright supporting portions 21b. The upright supporting portions 21b are raised from the outer-circumferential edge of the ring-form body 21a and are lined up side by side at equal angular intervals. The inner cutter bodies 23 are formed on the tip ends of the respective upright supporting portions 21b. 
The root portions of the adjacent upright supporting portions 21b on the side of the ring-form body 21a are connected to each other within a specified height range Y from the surface of the ring-form body 21a so that the overall shape is formed as a cylindrical shape. Accordingly, the bottom surface portion of each inner cutter 20 is constructed in the shape of a dish by the root portions of the respective upright supporting portions 21b formed into a cylindrical shape, and the ring-form body 21a. 
Furthermore, the inner cutter bodies 23 are integrally connected to the inclined surfaces of the upper portions or the respective upright supporting portions 21b (which are formed with a triangular shape, as one example) so that the inner cutter bodies 23 protrude to the outside of the corresponding inner cutter 20. The tip ends of the inner cutter bodies 23 are formed with a bifurcated shape, so that the overall shape of the inner cutter bodies 23 is a U shape or Y shape. Of the bifurcated tip ends of each inner cutter body 23, the tip end on the outer-circumferential side contacts the inside surface of the outside hair introduction region V of the corresponding outer cutter 18, while the tip end on the inner-circumferential side contacts the inside surface of the inside hair introduction region W of the corresponding outer cutter 18. When the outer cutters 20 rotate, the respective tip ends of the respective inner cutter bodies 23 rotate while making sliding contact with the inside surfaces of the respective hair introduction regions V and W of the corresponding outer cutters 18.
Furthermore, the inner cutters 20 are attached to the inner cutter bases 22 by the insertion of the tip ends of the inner cutter bases 22 into opening parts opened in the bottom surfaces of the ring-form bodies 21a of the inner cutters 20. Accordingly, these opening parts of the inner cutters 20 are closed off by the inner cutter bases 22.
The cutter retaining plate 34 is a component that holds the inner cutters 20; this cutter retaining plate is formed from a synthetic resin material, and is constructed from attachment rings 34a that are equal in number to the inner cutters 20, and a supporting frame 34b which connects these attachment rings 34a into an integral unit. Furthermore, anchoring portions 48 protrude toward the axial lines of the attachment rings 34a from the inner-circumferential surfaces of the attachment rings 34a. Furthermore, an attachment screw 50 which is used to attach the cutter retaining plate 34 to the cutter frame 30 is disposed in the center of the cutter retaining plate 34.
The structure by which the inner cutters 20 are held by the cutter retaining plate 34 will be described.
The inner cutter bases 22 to which the inner cutters 20 are fastened are formed in a columnar shape from a synthetic resin material. An inner cutter 20 is fastened to one end portion (the upper end portion in FIG. 8) of each inner cutter base 22, and a flange part 52 is formed on the outer-circumferential surface of the other end portion (the lower end portion in FIG. 8) of each inner cutter base 22. Furthermore, a positioning engaged portion 38 (as one example, this part is formed as an engaging projection) which engages with a positioning engaging portion 36 formed in the center of the corresponding outer cutter 18 is formed in the center of the first end portion of each inner cutter base 22. Moreover, the radius of the flange parts 52 of the inner cutter bases 22 is greater than the distance from the axial lines (centers) of the attachment rings 34a to the inside tip ends of the anchoring portions 48 formed on the inner-circumferential surfaces of the attachment rings 34a, and the radius of the parts of the inner cutter bases 22 other than the flange parts 52 is smaller than the distance from the axial lines of the attachment rings 34a to the inside tip ends of the anchoring portions 48. Furthermore, engaging recesses 56 in which engaging projections 54 formed on the tip ends of the inner cutter drive shafts 28 are engaged are formed in the end surfaces of the second end portions of the inner cutter bases 22.
Furthermore, when the inner cutters 20 are fastened to the inner cutter bases 22, the ring-form bodies 21a of the inner cutters 20 are first fastened to the first end portions of the inner cutter bases 22, and the inner cutters 20 are fastened to the inner cutter bases 22. As a result, the positioning engaged portions 38 protrude from the insides of the ring-form bodies 21a. 
Afterward, the inner cutter bases 22 are inserted into the attachment rings 34a of the cutter retaining plate 34 from the other end portions of the inner cutter bases 22. In this case, the anchoring portions 48 of the attachment rings 34a and the flange parts 52 of the inner cutter bases 22 interfere with each other; however, the anchoring portions 48 are caused to bend slightly, thus allowing the insertion of the flange parts 52 into the attachment rings 34a. 
As a result, the inner cutters 20, whose radii are greater than the distance from the axial lines of the attachment rings 34a to the inside tip ends of the anchoring portions 48, and the flange parts 52 of the inner cutter bases 22, are positioned on both sides of the attachment rings 34a with the attachment rings 34a clamped between these parts. Accordingly, the inner cutters 20 are held in the attachment rings 34a so that the inner cutters 22 are prevented from slipping out. Furthermore, the inner cutters 22 are held so that they are rotatable inside the attachment rings 34a, and so that they are tiltable in all directions with respect to the axial lines of the attachment rings 34a and free to slide in the direction of these axial lines.
Next, the structure used to attach the outer cutters 18 and inner cutters 20 to the cutter frame 30 will be described.
First, the outer cutter holder 32 to which the outer cutters 18 are attached is mounted in the cutter frame 30. Afterward, the cutter retaining plate 34 holding the inner cutters 20 is attached to the cutter frame 30 by screwing an attachment screw 50 into a female screw hole 30a formed in the inside surface of the cutter frame 30. As a result, the outer cutter holder 32 is pressed by the cutter retaining plate 34 so that the outer cutters 18 and inner cutters 20 are attached to the cutter frame 30 in a manner that prevents these cutters from slipping out.
Furthermore, if the attachment screw 50 is turned in the reverse direction, the inner cutters 20 can be removed from the cutter frame 30 as an integral unit with the cutter retaining plate 34, and the outer cutters 18 can be removed from the cutter frame 30 as an integral unit with the outer cutter holder 32.
Next, the main body case 16 in which the inner cutter drive shafts 28 are disposed will be described.
The main body case 16 is formed in the shape of a cylinder with a bottom, which is open at the top. A motor 12, a battery (not shown) and a control circuit, etc., are contained inside this main body case 16.
A gear bearing plate 58 is disposed inside the main body case 16 near the edge of the opening of the main body case 16. The motor 12 is fastened to this gear bearing plate 58 at right angles in a state in which the output shaft 12a of the motor 12 is caused to protrude. Furthermore, supporting shafts 60 are fastened in place adjacent to the output shaft 12a and parallel to the output shaft 12a in positions corresponding to the outer cutters 18. Moreover, a motor gear 62 is attached to the output shaft 12a, and inner cutter driving gears 64 made of a synthetic resin are attached to the supporting shafts 60 so that these inner cutter driving gears 64 are rotatable, and so that the gears 64 engage with the motor gear 62. Cylindrical cover portions 65 which cover the supporting shafts 60 that are passed through the inner cutter driving gears 64 are disposed in upright positions as integral parts of the inner cutter driving gears 64 on the central portions of the upper surfaces of the inner cutter driving gears 64, and shaft anchoring portions 70 are formed so that these shaft anchoring portions 70 surround the cover portions 65.
Furthermore, a cutter cradle 26 which closes off the opening part at the upper end of the main body case 16 is positioned above the gear bearing plate 58 in the opening part. Drive shaft holes 66 are formed in this cutter cradle 26 coaxially with the respective supporting shafts 60 on the axial lines of the supporting shafts 60.
The inner cutter drive shafts 28 are disposed so that the tip ends of these inner cutter drive shafts 28 protrude from the drive shaft holes 66. A plurality of engaging projections 68 are formed on the outer-circumferential surfaces of the lower ends of the inner cutter drive shafts 28, and these engaging projections 68 respectively engage with the plurality of shaft anchoring portions 70 that are formed on the upper surfaces of the inner cutter driving gears 64 so that these anchoring portions 70 surround the lower parts of the inner cutter drive shafts 28.
More specifically, the inner cutter drive shafts 28 are provided so that: the inner cutter drive shafts 28 rotate as an integral unit with the inner cutter driving gears 64, the inner cutter drive shafts 28 tilt in all directions with respect to the axial lines of the inner cutter driving gears 64 (which are also the axial lines of the supporting shafts 60), and the inner cutter drive shafts 28 move a specified distance along these axial lines.
Engaging projections 54 are formed on the closed upper ends of the inner cutter drive shafts 28, and the lower ends of these inner cutter drive shafts 28 are formed as open cylindrical bodies. The cover portions 65 formed on the inner cutter driving gears 64 are inserted into the interiors of the inner cutter drive shafts 28 from these opening parts at the lower ends of the inner cutter drive shafts 28.
Furthermore, coil springs 72 are disposed inside the inner cutter drive shafts 28 so that the coil springs 72 are fitted over the cover portions 65. These coil springs 72 are disposed so that they are compressed between the inside upper surfaces of the inner cutter drive shafts 28 and the upper surfaces of the inner cutter driving gears 64; accordingly, the inner cutter drive shafts 28 are constantly driven upward with respect to the inner cutter driving gears 64. The inner cutter drive shafts 28 are driven by the coil springs 72 in a direction that causes the inner cutter drive shafts 28 to move away from the inner cutter driving gears 64. However, when the inner cutter drive shafts 28 are away from the inner cutter driving gears 64 by a specified distance, the engaging projections 68 formed on the outer-circumferential surfaces of the lower ends of the inner cutter drive shafts 28 engage with the shaft anchoring portions 70 formed on the upper surfaces of the inner cutter driving gears 64. Accordingly, the inner cutter driving gears 64 do not slip off of the cover portions 65.
With the above-described structures of the cutter head section 24 and main body case 16, when the cutter head section 24 is attached to the main body case 16, the engaging projections 54 formed on the tip ends of the inner cutter drive shafts 28 are inserted into the engaging recesses 56 formed in the lower end surfaces of the inner cutter bases 22. Furthermore, the inner cutter drive shafts 28 are pressed against the inner cutter bases 22. Thus, the inner cutter drive shafts 28 are pushed slightly into the interior of the cutter cradle 26 against the driving force of the coil springs 72.
In this state, the driving force of the coil springs 72 is transmitted to the inner cutters 20 from the inner cutter drive shafts 28 via the inner cutter bases 22, so that the inner cutters 20 are pushed toward the outer cutters 18. As a result, the tip ends of the inner cutter bodies 23 of the inner cutters 20 contact tightly to the inner-circumferential surfaces of the outer cutters 18, and the outer cutters 18 are pushed by the inner cutters 20 so that the outer cutters show a maximum protrusion from the cutter frame 30.
Then, when the electric shaver 10 is used to shave hair, the main body case 16 is held in the hand, and the outer cutters 18 that protrude from the surface of the cutter frame 30 are contacted to the skin. In this case, the outer cutters 18 move into the interior of the cutter frame 30 against the driving force of the coil springs 72 and the elastic force of the cutter retaining plate 34 (i.e., the amount of protrusion of the outer cutters 18 from the cutter frame 30 changes), or the outer cutters 18 tilt appropriately, in accordance with the contour of the skin. As a result, the respective hair introduction regions V and W formed in the outer cutters 18 are maintained in tight contact with the skin.
Even in cases where the outer cutters 18 tilt with respect to the cutter frame 30, the positioning engaged portions 38 formed on the end portions of the inner cutter bases 22 are engaged in an interlocking manner with the positioning engaging portions formed on the outer cutters 18. Accordingly, the inner cutters 20 also tilt in accordance with the tilting of the outer cutters 18. Thus, the respective tip ends of the inner cutter bodies 23 of the inner cutters 20 are kept in tight contact with the inside surfaces of the respective hair introduction regions V and W of the outer cutters 18.
The hair cut by the inner cutters 20 and outer cutters 18 working together are taken into the insides of the outer cutters 18 and fall downward through the rotating regions of the inner cutter bodies 23. Ultimately, the hair accumulates on the surface of the synthetic resin cutter cradle 26 which is attached so that it covers the opening part formed in the upper portion of the main body case 16.
However, the hair that has been cut is very fine. Thus, not all of hair falls downward through the rotating regions of the inner cutter bodies 23. In many cases, the hair is caused to advance toward the center, i.e., into the internal regions of the inner cutters 20, by the eddy-form air currents that are generated inside the outer cutters 18 by the rotation of the inner cutters 20. The hair that has thus entered the internal regions of the inner utters 20 move toward the bottom portions of the internal cutters 20. However, the structure of the bottom portion of each inner cutter 20 is constructed as described above in the form of a dish by the root portions of the respective upright supporting portions 21b that are formed into a cylindrical shape as a result of being connected to the ring-form body 21a. Thus, the hair has no avenue of escape. As a result, hair 73 accumulate on the inside bottom surfaces of the inner cutters 20 (i.e., on the upper surface of the ring-form bodies 21a, and especially in the corner areas with the upright supporting portions 21b on the outer-circumferential edge as shown in FIG. 9C). Furthermore, unlike the upper surface of the cutter cradle 26, which is inherently set so that hair will accumulate, the insides of the inner cutters 20 in which the hair accumulates are not designed for ease of cleaning. Thus, it is difficult to clean away the hair in the inner cutters 20.
Accordingly, the object of the present invention is to solve the above-described problems in the prior art inner cutters in electric rotary shavers.
More specifically, the object of the present invention is to provide an inner cutter for an electric rotary shaver, as well as an electric shaver, which prevents the accumulation of hair, beard, mustache, etc. (referred to as xe2x80x9chairxe2x80x9d) inside the inner cutter even if shaved hair should advance into the interiors of the inner cutter.
The above object is accomplished by a unique structure for an electric shaver and particularly for an inner cutter for an electric shave, in which the inner cutter comprises:
a cutter supporting member that has a ring-form body formed in a shape of a flat plate and a plurality of upright supporting portions which rise from an outer-circumferential edge of the ring-form body and are lined up side by side; and
an inner cutter body that is formed on the tip end of each one of the upright supporting portions, wherein
the upright supporting portions are formed with gaps between adjacent upright supporting portions, and
the adjacent upright supporting portions are connected to each other by ribs at positions that are away from the ring-form body.
As a result, even if shaved hair advance into the interior of the inner cutter and fall on the surface of the ring-form body, the hair can escape to outside of the inner cutter via the gaps between adjacent upright supporting portions, and more particularly, via the gaps defined by the ribs, the adjacent upright supporting portions and the outer edge of the ring-form body. Accordingly, the cut hair is prevented from accumulating inside the inner cutter.
In the above structure, in each of the upright supporting portions, the width of the lower half thereof is formed smaller than the width of the upper half thereof. In other words, a part of each upright supporting portion that is located on one side (lower side) of a position where the ribs are joined and is closer to the ring-form body is smaller than the width of a part of each upright supporting portion which is located on another side (upper side) of the position where the ribs are joined and is closer to the inner cutter body.
With this structure, the gaps through which the hair escape increase size-wise, and the cut hair is more easily discharged and even less likely to accumulate inside the inner cutter.
Furthermore, the inner cutter is formed by stamping and bending a single flat metal plate, and each of the ribs is bent outward from a central portion thereof so as to have a V shape.
As a result, the inner cutter is manufactured by pressing, and the manufacturing cost can be reduced.
The above described object is further accomplished by a unique structure of the present invention for an electric rotary shaver that comprises:
a main body case that contains an electric motor, and a cutter head section that is detachably mounted on an upper portion of the main body case, the cutter head section including outer cutters and inner cutters that shave hair in cooperation with the outer cutters while rotating in sliding contact with the outer cutters, wherein each of the inner cutters is comprised of:
a cutter supporting member that has a ring-form body formed in a shape of a flat plate and a plurality of upright supporting portions which rise from an outer-circumferential edge of the ring-form body and are lined up side by side; and
an inner cutter body that is formed on tip end of each one of the upright supporting portions, wherein
the upright supporting portions are formed with gaps between adjacent upright supporting portions, and
adjacent upright supporting portions are connected to each other by ribs at positions that are away from the ring-form body.
The above described object is further accomplished by another unique structure of the present invention for an electric rotary shaver that comprises:
inside outer cutters;
cylindrical outside outer cutters which surround the inside outer cutters in a concentric configuration, the cylindrical outside outer cutters being mounted inside a cutter frame so that tip ends of the outside outer cutters protrude together with the inside outer cutters from outer cutter holes formed in the cutter frame;
inside inner cutters that make a sliding contact with the inside outer cutters; and
outside inner cutters that make a sliding contact with the outside outer cutters, wherein
each of the outside inner cutters is comprised of:
a cutter supporting member that has a ring-form body formed in a shape of a flat plate and a plurality of upright supporting portions which rise from an outer-circumferential edge of the ring-form body and are lined up side by side, and
an inner cutter body that is formed on tip end of each one of the upright supporting portions, wherein
the upright supporting portions are formed with gaps between adjacent upright supporting portions, and
adjacent upright supporting portions are connected to each other by ribs at positions that are away from the ring-form body;
the outside outer cutters are provided inside the cutter frame so that the outside outer cutters are tiltable with respect to axial lines of the outer cutter holes and movable along the axial lines, and the inside outer cutters are connected to the outside outer cutters so that the inside outer cutters are tiltable with respect to axial lines of the outside outer cutters and movable along the axial lines;
the inside inner cutters are engaged with the inside outer cutters so that the inside inner cutters are rotatable in a state in which the axial lines of the inside inner cutters and the inside outer cutters constantly coincide; and
the outside inner cutters are engaged with the outside outer cutters so that the outside inner cutters are rotatable in a state in which the axial lines of both cutters constantly coincide.